Primary frequency regulation is an important means for frequency regulation of power grid. After the power grid frequency exceeds a preset dead zone, the steam turbine generator set releases boiler-stored heat via a fast-action regulating valve to change the mechanical work, to thereby change the mode of the active power.
Generally, there are two factors that decide the primary frequency regulation performance of a generator set: one is frequency regulation energy storage, and the other is fast release. If the generator set has sufficient energy storage, the exclusive factor deciding the fastness criteria (such as response time, rising time, etc.) of primary frequency regulation of the generator set is for the executing mechanism to fast release the energy storage.
In the prior art, primary frequency regulation of a thermal generator set is usually designed by the following principles:
(1) Designing requirements at the digital electric hydraulic control system (DEH) side: a designing process is employed whereby a speed difference signal is directly superimposed at the speed regulation valve instruction of a steam turbine (combustion engine) via a speed governing droop design function. Simultaneously, the power instruction of the DEH power circuit also compensates a frequency regulation power fixed value according to a speed governing droop design criteria, and the compensated frequency regulation power fixed value is not restricted by the speed, as shown in FIG. 1.(2) Requirements at the coordination control system (CCS) side: a generator set employing distribution control system (DCS) and having coordination control and AGC functions completes the primary frequency regulation function by DEH together with CCS; a designing process is employed at the DEH side whereby a speed difference signal is directly superimposed at the speed regulation valve instruction of a steam turbine (combustion engine) via a speed governing droop design function, while a frequency correcting circuit is designed in the CCS, and the correction instruction in the CCS is not restricted by the speed, as shown in FIG. 2.
By virtue of the aforementioned design, it is possible for the thermal generator set to achieve fastness of primary frequency regulation through the functions at the DEH side, and achieve constancy of primary frequency regulation through the design at the CCS side.
Although the primary frequency regulation function of a generator set is achieved in the typical designs shown in FIGS. 1 and 2, when the grid frequency slightly fluctuates, energy storage of the generator set usually cannot be effectively released because the action of the executor is extremely small or because there is dead zone of the action, and the design and assessment criteria of primary frequency regulation hence cannot be achieved, the typical solution fails to take into consideration the influence of slight fluctuation of the grid frequency against the realization of the primary frequency regulation function of the generator set.